The present invention is with respect to a process for testing the coagulation properties of a liquid and to a coagulation testing apparatus or coagulometer.
A great number of different ways of measuring the coagulation properties of liquids, as for example blood, or for measuring the time taken before coagulation takes place have been put forward. For a general overview of prior art systems for measuring the clotting properties of blood see, for example, the paper by F. P. Gauper with the title "Blutgerinnung--Methoden zur Erfassung des Gerinnungseintritts" in GIT-Fachzeitschrift fur das Laboratorium, 19th year, special issue 1975, pages 509 to 512.
In the last one or two years developments have more specially taken place with the purpose of effecting automatically measuring and recording the clotting or coagulation time. In some of such systems a ball or the like is placed in a measuring vessel, in which the blood is placed and which is turned or moved in some other way and the ball is kept by a force, such as a magnetic field or gravity, in a given position as desired, which is not dependent on the motion of the measuring vessel. At the start of clotting and forming of fibrin, the ball is moved as well by the motion of the measuring vessel because a fibrin structure is formed within the vessel. The point in time, at which the ball is moved out of the position it had in the first place, may be sensed optically, inductively, capacitively etc.
Such systems all have the shortcoming that, in addition to the measuring vessel, which is mostly only designed for use once and then thrown away, it is necessary to have a ball which is normally made with a high degree of accuracy so that it is not possible for it to be thrown away and in fact it has to be carefully cleaned after each measuring operation.
Furthermore, purely optical systems have been put forward in the prior art in which cloudiness produced when clotting takes place is sensed by a photoelectric detector system. Such a system may clearly only be used for testing plasma and not for natural blood.
Further prior art systems have been based on changes in the oscillation properties of a sample at the start of clotting. However such an apparatus has the shortcoming that, because of its high sensitivity, vibrations acting on the apparatus from the outside are likely to have an effect on it.